Organoboron compounds have broad applications in organic synthesis (Boronic acids, D. G. Hall, ed. Wiley-VCH, Weinheim, 2005), catalysis (P. A. Chase, et al., Angew. Chem. Int. Ed. 2007, 46, 8050; A. Staubitz et al., Chem. Rev. 2010, 110, 4079; W. E. Piers et al., Inorg. Chem. 2011, 50, 12252), optoelectronic devices (C. D. Entwistle et al., Angew. Chem. Int. Ed. 2002, 41, 2927; C. D. Entwistle et al., Chem. Mater. 2004, 16, 4574; Y. Shirota et al., Chem. Rev. 2007, 107, 953; F. Jäkle, Chem. Rev. 2010, 110, 3985; P. Chen, et al., Angew. Chem. Int. Ed. 2012, 51, 7994; C. Dou, et al., Angew. Chem. Int. Ed. 2012, 51, 12206; S. Saito, et al., J. Am. Chem. Soc. 2012, 134, 9130; Z. M. Hudson, et al., Dalton Trans. 2011, 40, 7805), sensors (C. R. Wade, et al., Chem. Rev. 2010, 110, 3958), and probes (G. Zhang, et al., Nature Mater. 2009, 8, 747; F. R. Kersey, et al., ACS Nano 2010, 4, 4989). Among π-conjugated organoboron compounds, azaborines (aromatic molecules wherein a C—C moiety has been replaced by a B—N moiety) have attracted much research interest. Such replacement of a C—C unit in an aromatic molecule with an isoelectronic B—N unit has been shown to impart interesting properties that are distinct from those of the C—C aromatic analogues. Such properties may include electronic, photophysical, luminescent, as well as chemical properties.
Examples of polycyclic π-conjugated azaborine molecules and derivatives remain rare, compared to the vast numbers of carbocyclic aromatic compounds and heterocyclic aromatic compounds. Known syntheses of azaborine compounds are challenging, and frequently involve multi-step reactions and/or use of transition metal catalysts. Development of efficient and simple synthetic methods for B—N substituted aromatic compounds is desirable to advance the chemistry and applications of this class of compounds. Photoelimination reactions are known for many organic compounds such as azo, azide and ketone compounds (W. H. Saunders, et al., Mechanisms of Elimination Reactions, John Wiley & Sons, New York, 1973; A. Gilbert, et al., Photochemistry, 1995, 26, 326). They are, however, rare for organoboron compounds (A. Pelter, et al., Tetrahedron, 2000, 56, 7339).